pregnancy tests are negative so what is it?

okay I'm starting to think I'm pregnant, only because i eat like crazy my breast and nipples hurt and I'm late on my period its been about 1 mouth and 2 weeks. iv taken pregnancy test but the all say no but sum times my period is not regular. There was a time i didn't have it for 6 mouths but at that time i didn't have symptoms... plus i don't have money to go to the doctors so i came here i want to no what u think is wrong with me?